Green River has gone deep into its back catalog in anticipation of its reunion performance Sunday (July 13) in Seattle as part of Sub Pop's 20th anniversary bash.

Green River has gone deep into its back catalog in anticipation of its reunion performance Sunday (July 13) in Seattle as part of Sub Pop's 20th anniversary bash.

Bassist Jeff Ament tells Billboard.com the group re-learned two unreleased songs from its early demo, "Baby, Help Me Forget" and "Leech," for the occasion, which will mark Green River's first show in nearly 21 years.

"In a weird way, those are probably some of the best songs we have," he says. "It's funny how it works. At the time, we thought they were way too simple or not challenging enough. But in retrospect, they're really great pop songs. We re-learned those two, but there are five or six songs that never got released."

Green River, which also includes Pearl Jam guitarist Stone Gossard, Mudhoney principals Mark Arm and Steve Turner and drummer Alex Vincent, rehearsed twice in late April but has reconvened three additional times to relearn the material.

"Last night, felt like we were 95% there," Ament says. "We had a go at 16 or 17 songs and we have 14 right now, but we may need to get that down to 11 or 12 for Sunday. We have a 40-minute slot."

Ament isn't ruling out the possibility of future Green River activity, saying, "It would be fun to write a couple of new songs with those guys." He admits the band has received offers to play live again, but his true goal is what he calls "the ultimate pairing: we need to go ask the Stooges to do 25 shows or something. For me, then it would be worth it."

On Saturday, Ament and Gossard will join their Pearl Jam bandmates for VH1's "Rock Honors" tribute to the Who. The group will debut a cover of the Who's "The Real Me" for the occasion.

"It's always cool to learn a song like that, which is so different than our own style," Ament says. "We've also never played with horns and a string section before, so that will be an added special thing for us."